So-called middle-age spread poses a real danger to health as people age, American research has found.

The study, conducted by a team at University of Washington in Seattle, found the regardless of a person's weight at age 50, if they gained 20 pounds or more they were three times more likely to develop diabetes than those who did not gain weight.

Those who were already classed as obese at age 50 and then gained a further 20 pounds were five times more likely to develop type two diabetes compared with those who were not obese and did not gain weight.

The findings are published in the Journal of the American Medical Association.

The study also found that people who gained weight around their middle also increased their risk of diabetes.

There area thought to be around two million people in Britain with diabetes, and type two is the most common form.

Lead author Dr Mary Biggs said: "The results of this study affirm the importance of maintaining optimal weight during middle age for prevention of diabetes and, while requiring confirmation, suggest that weight control remains important in reducing diabetes risk among adults 65 years of age and older."